Sound absorbing structure



July 12, 1960 M. DoBBlNs SOUND ABsoRBING STRUCTURE Filed Jan, 28, 1957 INVENToR.

MARK ooBBlNs BY ATTOR EYS 76 FIG.7.

nite States Patent 2,944,622 SOUND ABSORBING STRUCTURE Mark Dobbins, Detroit, Mich., assignor to Fenestrzylncorporated, Detroit, Mich., a corporation of Michigan Filed Jam 28, 1957, SerfNo. 636,823

7 Claims. (Cl. isi-mss) The present invention relates to sound absorbing structure and more particularly, to insulating and sound absorbing pads used with acoustically treated metal ceiling panels to absorb sound.

` The present application is a continuation-in-part of my prior copending application Serial No. 583,235, filed May- 7, 1956, now abandoned. g y .Y

Metal' ceiling panels are acoustically treated byv per forating the panels to provide small apertures or perforaations in the metal so`that they are exposed to the room,v and by placing sound absorbing material over the panels to absorb sound waves that pass through the apertures. It is desirable that the sound absorbing m'aterialbe in a form that-will not allow loose particles to fallfthrough the apertures. It is also desirable that the sound absorbingl material be spaced rearwardly `from the apertures so f that the apertures will not become plugged, so that the sound absorbing material is notl Visible' to an observer standing o n the floor level, so as to facilitate maintenance such as washing or painting, and'so as to provide sound plenum which increases the soundabsorbing characteristics when the optimum Vspacing is used."

Heretofore, `in order" to accomplish -the foregoing it` was the practice in the industryto provide the sound absorbing material in the form'of fibrous pads and'to supf' o port these pads on a Wire grid or wire chair.

'It isan object of the present invention to provide sound absorbing material, for use with metal ceiling panels, the material being molded from a fibrous batt into a pad having outstanding legs along each lateral edge for' supporting the pad and for spacing the intermediate portion of the pad away from the perforations in thepanel and which, because of the resulting arched configuration, provides a greater surface area exposed to the sound waves, thus increasing the surface of the pad while still maintaining the pad housing dimensions.

It is a furtherobject of Ithe present invention to provide a sound absorbingtpad of molded construction having outstanding legs `along each lateral edge with the materialin `each leg being compacted to stiffen and strengthen the leg.A

. 'More specifically, it is an object of the present inyenunit type acoustical pan system;y .l

Figure 5 is an enlarged fragmentary sectional View;

showing the'relationship between the edge of a pad and the housing. v

Figuresv and 7 are diagrammatic sectional views showing end modifications of pads.

' Referring now to the drawing, a pad of sound absorb in g material is generally indicated at 10.. The pad is in aV molded form of generally rectangular cross-sectional shape having a flat intermediate portion 12 and provided with taperedinclined edge lportions providing .supporting legs 14 terminating ink rounded feet 16. In accordance with the preferredembodiment of the invention, the pad.

is fabricatedfrom fibrous material although any suitable equivalent material may be employed. Excellent results havebeen obtained when the pad is fabricated from glass diameter of the fibers is generally within the lrange fibers, which have excellent sound absorbing properties, and when lightly impregnated with a suitable binder such as aphenolic resin are readily moldable to the desired form;V Excellent results have been obtained. 'when the of from .OOOl'to .0004 inch.

*In fabricating the pad, an Velongatedbattofthe bers is 'laid-up in parallel layersso that the layers lhave a horizontal orientation as indicated Iby the lines'18 .`"rT:`he unidirectional properties of the layers of fibers give the ma= teial resiliency4 inadirection perpendicular to thehorif zontal arrangement of the fibers.

The strength ofthe pad of course varies with thedensity of the fibers, being higher when the density of the fibers is greaten Ina specific example which has established its utility in practice, pads lare produced from glass fiber batts having an vinitial thickness Iof about 11/2 inches and being loosely varranged to be of about'one pound per cubic `foot density. The fibersl rare provided with a` suitable binder, such for example as a light distribution of a phenolic-resin therethrough whereby on compression of the fibers the surface strata thereof are bonded together. The. resin is provided in a quantity sufficient to produce the required binding action without at the same time substantially interfering .with the tion to providea pad as defined in the'. preceding paragraph inwhich the legs are tapered to provide 4gradually increasing density, stiffness and strength,v

Itis a further object of the present invention Yto provide anovel method of producing. sound absorbing pads which comprises molding a batt of loosely arranged fibrous material having a binder therein and of generally rectangular cross-section to provide an intermediate partially compressed flat portion, shaping the edge portions of the batt to provide gradually tapered legs of increasing density yandfstrength, and causing the edge portions to extend beyond one side of the batt to form supporting legs.

Other objects-and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawporosity and sound absorbing properties of the pad.

In this condition the batt is molded between relatively movable die membersto have the .c-ross4sectional shape illustrated in the figures, the edge portions'of the 'batt being tapered and vat the Sametime shaped to incline tow-ard and extend beyond one side of the batt so as to produce 'the' supporting'legs 14. Due to the" relatively greater yincreasing compression ofthe` fibrous material towards the'edges of the pad, the legs are ofrincreasing density and hence of increasing strength, the extreme edge portions ofi-the pad thusprovidinjg relatively hard, strong Iand dense supportingtfeet well adapted to resisty Wear. As best seen in Figure 3, it will be apparent that the tapered shape of the legs is such .as to provide a thickness thereof at a point adjacent the extreme ends of the legs less than half the thickness of the intermediate 'portion of the pad. The compression existing at the extreme edge portions of the pad is of course even vPatented July 12, 1960.

upon completion of the molding process the acoustical pad is in its finished condition.

The molding operation is carried out so as to produce some reduction in thickness of the intermediate portion of the batt. Excellent results have been `obtained when the thickness of the intermediate portion of the 'batt is redluced from about 11/2 inches to one inch inthe finished pa and primarily at the top and bottom surfaces of the batt, the finished pad is of unequal density andthe surface strata of the pad are somewhat compacted forming a shell-like surface providing ext-ra strength. This shell tends to prevent separation of individual fibers from the pad and so prevents shifting of the fibers which might .otherwise tend to close or reduce the effective `area of the perfor-ations inthe panel.

Accordingly, the pad, while of no very great strength, is nevertheless 4form-sustaining and self-supporting, the self-supporting property being attributable largely to the provision of the relatively denser and gradually compacted tapered supporting legs. Moreover, these legs terminate in rounded still further densified support-ingy feet well ladapted to resist wear while in contact with supporting surfaces.

In Figures 2 and 3 the pads are shown as received in hollow acoustically treated metal ceiling panels 20 corn-Y prising hat-shaped portions 22 attached to fiat plates 24 `as by spot welding at 26 along the anges 28. The plates 24 are perforated as indicated at 30 to allow sound waves to enter the chamber 32. The pad is inserted through the open end and into the chamber 32 with the legs `14 extending downwardly and the -feet 16 resting on the upper surface of the plate 24.

It will be observed in Figure 2 that the portions of the plate 24 just linwardly from the side walls of the hat section 22 have no perforations and thus constitute imperforate supporting ledge portions upon which the foot portions of the pads rest.

When installed in the panels the foot portions 16 ofthe pad space its lower surface 34 upwardly from the. upper surface of the plate 24, thus forming a plenum chamber `and preventing blocking of the per-forations 30 to allow sound waves to enter the plenum and to strike the pad to be absorbed thereby. i

another embodiment of the present rinvention which comprises a pan 40 having `a perforated bottom wall 42, the

' perforations being spaced from the edges to leave im perforate ledge portions 44. The pan has upwardly ex-V tending side walls 46 which may have indented grooves or Vchannels 4S for erection, and which .are open at the top. In this embodiment of the invention, the pad herein designated 50 has downwardly and outwardly inclined tapered edge portions 52 terminating in rounded feet portions 54 resting upon the imperforate ledge portions 44 to support the body of the pad 50 above the perforated portion of the bottom wall 42. This leaves a space 56 therein above the bottom wall v42 and prevents the pad from closing any of the aperatures. Inthis case the' edge portions 52 of the pad are preferably continuous around all four sides of the pad 50.

Referring now to Figures 6 4and 7 there are illustrated modified pad constructions applicable particularly to the arrangement ofv Figures 1 3.V In this case the panels 20 may be very long and it is` contemplated that the pads 10 will be' provided in much shorter length, such for example only a few feet. Thus, la plurality of pad sections will be required to fil-l one panel vfrom end to end. In VFigure 6 there is illustrated one form of interfitting ends provided on the acoustical pads. In this figure each pa-d section has a concave V-recess 60 at one end and a convex V-shape 62 at the other, the two interfitting as shown. This prevents direct passage of sound waves through the spaces above the pads in the panels 20'. Normally, the pads may be assembled only by sequential insertion from one end. If desired, some mechanical Inasmuch as this compression takes place initially.

T" interconnection between adjacent pads may be provided as by pointed pins 6d inserted as the pads are inserted.

In Figure 7 a similar arrangement is shown, the pads 70 Aand 72 having tongue and groove end portions 74 and 76 respectively, adapted to interfit on assembly. v In all embodiments of the invention it will be apparent that the area of the surface of the pad available for absorbing incidental sound `waves within the pad is substantially increased by the arched construction providing a concave surface exposed to the sound. Thus, the arched configuration of the pad not only provides for suitable support of the pad without the necessity of the wire grids or chairs previously used, but 4also actually improves the efficiency in a pad provided in a panel olf a given size due to the increase in `area of sound absorbing material exposed to the sound.

The production of the acoustical pads from a batt of generally rect-angular cross-section having a preferably thermo-setting Ybinder therein provides for the production of pads on the most economical basis possible.

Moreover, these pads are produced by a novel method,l

o-f molding the pads in a manner to provide some cornpression throughout the entire surface of the batt so asV to form a shell-like structure, with increasing compres-` sion and :densific-ation of the tapered leg portions to provide relativelystrong, durable pad supporting legs.

In the specific example described in the foregoing, it will be recalledthat the fibrous material of the batt before compression and moldingto the desired shape of Referring now to Figures 4 and 5y there is illustrated f the pad was of about one pound density. Since the intermediate portion o-f the pad is reduced in thickness from yapproximately 11/2 to about one inch, it will be appreciated that the average density of the fibrous material in the intermediate portion of the pad between the supporting legs in the completed pad is about 11/2 pounds. Average density `is `referred to since the operationdescribed above results in effecting a compacting action of strata adjacent the top `and bottom surfaces of the pad to a greater extent than portions located ygenerally midway between theltop and bottom surfaces.` Y

It will be observed that the pad has the general configuration of an elongated body having Ia width severalv times its thickness. Accordingly, the ybody may be considered Ias having opposed fiat sides, ends, andedges. Thus, where the edge portions are defined as inclined to extend beyond one side surfaceof the pad, a side surface such Ias the side 34 in Figure 3. is intended.

The drawings and the foregoing specification constitute a description of the improved sound absorbing structure in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated b-y the appended claims.

What I claim as my invention is:

l. A sound absorbing member for use in 'a hollow panel having a perforated lower wall, said member being a unitary elongated body composed of loosely aggregated fibers lightly held together in form-sustainingrelation, the upper and lower surfaces ofV said body along the edge portions thereof extending downwardly fromV lan inter- `mediateportion Vof said body and forming supporting leg` portions for said member, -said downwardly extending leg portions having substantially* greater density .than the density of the intermediate portion of the member between said legs.

2. A sound absorbing member-for use in a hollow panel having a perforated lower wall, said member beingv a unitary elongated body composed in its entirety of loosely aggregated fibers lightly bonded together in form- 3. A sound absorbing member as set forth in claim 2 wherein the downwardly extending edge portions of the upper land lower surfaces of said 'body converge toward each other outwardly of the sound absorbing member.

4. A sound absorbing member as set forth in claim 2 wherein the edge portion of the upper and lower surfaces of said Abody extend outwardly as well as downwardly from the intermediate portion of said body and converge toward each other outwardly of the sound absorbing member.

5. A sound labsorbing member as set forth in claim 2 wherein the density o-f the fibers in said intermediate portion and legs is substantially inversely proportional to the thickness thereof.

6. A sound absorbing member as set 'forth in claim 2 wherein the density of the fibers in the intermediate portion of said member is about ll/z pounds per cubic foot.

7. A sound absorbing member as set forth in claim 2 wherein the surface portions of said body have an ap- References Cited in the le of this patent UNITED STATES PATENTS Andrews Jan. 13, 1925 Upson Aug. 30, 1932 Slidell Feb. 26, 1935 Morey Nov. 21, 1939 Wagner Jan. 16, 1940 .Meginnity Aug. 18, 1942 Burt Dec. 17, 1946 Milnor July 1, 1947 Willey et al. Ian. 11, 1949 Davies Apr. 24, 1951 Bush June 17, 1952 Alexander Sept. 13, 1955 Jones May 29, 1956 Gruber et al. Aug. 4, 1959 

